The objectives of this project are to clarify differences among several methods for measuring the same immunological parameter(s) and to find the most sensitive and reproducible test method(s) for assessing immunotoxicity and altered host resistance in order to define a testing battery. We are presently developing, refining and applying methods for measuring delayed hypersensitivity as well as T-lymphocytes, B-lymphocytes, macrophages and bone marrow cell functions to define chemical-induced immunotoxicity and altered host resistance using suspect or known immunotoxicants. Included in this effort are the validation and confirmation of the sensitivity of the selected methodologies using environmental chemicals suspect of altering the immune system. These studies will hopefully allow correlations between changes in immunological parameters to provide prognosticators of alterations in host resistance to bacteria, viruses, parasites or transplantable tumor cells.